<em># 声明焦点事件</em>
<tt>FocusNode</tt> <i>_focusNode</i> = <em>new</em> <q>FocusNode( )</q>;
<u>@override</u>
<tt>void</tt> <u>initState( )</u> {
	<i>_focusNode</i>.<s>addListener</s>(( ){
		<u>if</u> (<i>_focusNode</i>.<s>hasFocus</s>) { <em>// 得到焦点</em>	} <u>else</u> { <em>// 失去焦点</em>	}
	});
	<em>super.initState()</em>;
}
<em># 销毁和清除焦点</em>
<u>@override</u>
<tt>void</tt> <u>dispose( )</u> {
	<i>_focusNode</i>.<b>unfocus( )</b>;
	<em>super.dispose()</em>;
}
<em># 使用</em>
<u>C</u>(
	<s>focusNode</s> : <i>_focusNode</i>
)